Two-way sync between iCal and Google Calendar

How do I get two-way sync between iCal and Google Calendar. Currently, Google Calendar will populate iCal, but all of my appointments in iCal are not populating Google Calendar.

Just to let you know what I have done. I have Mountain Lion. Went to iCal Preferences, added Google Calendar (tried it with Automatic and Google), tested adding an appt in GCal and it showed up in iCal. (Nothing showed up in GCal except the one I added.) Restarted both. Restarted laptop.

What am I doing wrong? Thanks!